Periodic Table & Trends

Question 1

What are the two major factors that contribute to periodic trends?

Answer 1

1. As you move from left to right, effective nuclear charge increases
2. As you move from top to bottom, radius of the valence shell increases moving further away from the nucleus

Question 2

Which periodic trends are determined by effective nuclear charge?

Answer 2

1. Ionization energy
2. Atomic radius
3. Electron affinity

Question 3

What is the atomic radius its trend?

Answer 3

Distance from center of nucleus to exterior of valence electron cloud. Radius decreases as you move up and to the right

Question 4

What is ionization energy, its units, and its trend? How is its trend different?

Answer 4

Ionization energy is the energy measured in kJ/mol required to remove the outermost electron from an atom. It increases as you move up and to the right. Compared to electronegativity, ionization energy trend is very erratic because it accounts for half-filled and filled orbital stability

Question 5

What is electron affinity, its units, and its trend?

Answer 5

Electron affinity is the energy (kJ/mol) absorbed (endothermic) or released (exothermic) when an electron is added to the valence shell of an atom. It increases as you move up and to the right

Question 6

What is electronegativity and its trend?

Answer 6

Electronegativity is the willingness of an atom to gain and retain an electron from a neighboring atom in a covalent bond. It increases are you move up and to the right

Question 7

What is the general principle behind the exceptions to the general trends? What two trends do they effect?

Answer 7

Half or completely filled subshells - electron affinity and ionization energy

Column with nitrogen vs. column with oxygen: nitrogen has all of its p orbitals half-filled, therefore, it requires greater energy to remove an electron (ionization energy) and when an electron is added less energy will be given off, if any (electron affinity)

Question 8

What is the general rule regarding the atomic size of cations and ions?

Answer 8

Generally, cations are smaller than neutral and anions due to less electron repulsion. Anions are larger than neutral atoms and cations due to greater electron repulsion

Question 9

What has a greater atomic radius, hydrogen or helium?

Answer 9

Hydrogen has smaller radius. The electrons in the helium atom are so close together that it causes repulsion

Question 10

What is the relationship between bond length and atomic radius?

Answer 10

The more tightly held the valence electrons are to the nucleus (shorter atomic radius) the shorter the bond will be between two atoms. Shorter bonds are stronger bonds

Question 11

What are the two exceptions to ionization energy?

Answer 11

Half or completely filled subshells

Question 12

What is the relationship between ionization energy and oxidation/reduction potentials?

Answer 12

MORE NEEDED ON THIS

Question 13

Why is second ionization energy always greater than first ionization energy?

Answer 13

Electrostatics - removal of second electron is more difficult due to stronger

Question 14

Higher electron affinity is associated with a more negative or positive energy?

Answer 14

Negative energy. A higher affinity means that the atom becomes more stable upon an addition of an electron to its valence shell, thereby releasing more energy (exothermic). Higher electron affinity is associated with a more negative energy

Question 15

How is electronegativity measured? How is bond determined to be ionic or covalent?

Answer 15

Pauling Scale is measured from 0.9 for Na and 4.0 for F. A bond is determined to be ionic if the electronegativity difference of the atoms is greater than 2.0 and covalent if less than 2. For those bonds that are between 2 and 1.5, they are said to be polar covalent. Below 1.5 is nonpolar covalent

Question 16

How is chemical reactivity of an atom determined?

Answer 16

Atoms of the same family (column) have similar reactivity because they have the same valence electrons

Question 17

What is the name of the family containing oxygen

Answer 17

Chalcogens

Question 18

Why are alkali metals strong reducing agents?

Answer 18

By losing their only valence s electron, they obtain a complete octet, stabalizing the atom.

Question 19

Why does the reactivity differ between alkali metals? In presence of molecular oxygen, what effect do the differences of reactivity have on the formation of oxides?

Answer 19

Ionization energy decreases as more shells are added to an atom. As you move down the alkali family, its easier to lose an electron thus becoming a more reactive species. As you move down the family/group, the elements become more corrosive/susceptible to oxidation. This can be seen by the different oxide formations and the stoichiometric relationships in the reactions.

Question 20

What is the product of mixing solid alkali metal and water?

Answer 20

Metal hydroxide + hydrogen gas

Question 21

What are the three different oxides that alkali metals form and why do they differ?

Answer 21

1. 4 Lithium atoms + 1 molecule O2 –> 2 molecules Li2O(s) [oxide[
2. 2 Sodium atoms + 1 molecule O2 –> 1 molecule Na2O2 [peroxide]
3. 1 K, Rb, Cs(s) atom + 1molecule O2 –> MO2 [superoxide]

Question 22

Why would diatomic nitrogen corrode lithium metal moreso than diatomic bromine?

Answer 22

Diatomic nitrogen has a stronger reduction potential than bromine does. This is required because, relative to the elements down the alkali family, lithium does not have a strong oxidation potential, requiring a species with a strong reduction potential in order for the reaction to occur.

Question 23

For bromine to become reduced, which metal would be the better reducing agent?

Answer 23

Because bromine’s reduction potential is not that strong relative to the other halogens, it requires a metal with a strong oxidation potential. Oxidation potential increases as you move down the alkali metal family. Cesium is stronger than Rubidium and Potassium in terms of oxidation potential. Therefore, for bromine to react, Cesium would be the best choice.

Question 24

Of the alkali metals, which are the stronger reducing agents?

Answer 24

The oxidation potential increases as you move down the alkali family due to increase shielding

Question 25

What is the solubility of alkali and alkaline earth metals in water?

Answer 25

Alkali metals are soluble in water but alkaline earth metals are not.

Question 26

How do alkaline earth metals compare to alkali metals in terms of reactivity/oxidation?

Answer 26

Alkaline earth metal have the same trends as alkali metals but are not as strong as reducing agents due to their stronger effective nuclear charge. Comparing elements of the same period, the alkaline earth metal will have a lesser oxidation potential

Question 27

What is unique about beryllium?

Answer 27

Berylllium forms covalent bonds not ionic bonds due to their small size and effective nuclear charge

Question 28

Chalcogens are consisted of what types of elements? What is the reactivity trend of this elements? Solubility?

Answer 28

Nonmetals and metalloids. Oxygen and sulfur are nonmetals whereas selenium, tellurium, and polonium are metalloids. Reactivity decreases as you move down the family. They are usually nonsouble in water

Question 29

How do the chalcogens exist in nature? What is their structure? Are they all diatomic?

Answer 29

Oxygen exists in a diatomic state. Sulfur and Selenium exist in an octameric state, telenium and polonium exist in molecular matrices